03/22/1994

AAES Publishes Handbook on Shade Trees for the Southeast

AUBURN, Ala. - As the temperature rises in Alabama, planting shade trees seems like a better and better idea. But which trees grow fastest? Which have the best spring flowers and fall colors? Which have disease problems or are not suitable to Alabama's climate?

Backyard landscapers and professional foresters alike will find the answers to these and other questions in Shade Trees for the Southeastern United States: An Auburn University Evaluation, a book recently published by the Alabama Agricultural Experiment Station (AAES). Written by a team of researchers in the AU Department of Horticulture, this reference manual is designed for landscapers, students, nursery operators, master gardeners, urban foresters, garden center owners and anyone who enjoys trees.

"Increased emphasis on tree plantings in cities and residential areas has accelerated the introduction of new trees to the ornamental industry," said David Williams, an assistant professor of horticulture and co-author of the book. "Unfortunately, many of these new species are selected for landscape use before adequate information is available. Information on the regional adaptability of new species is especially lacking."

Lack of information has led to the use of trees that are unsuited to Southern landscapes, resulting in poor tree performance, high maintenance costs or costly removal expenses, Williams added. For example, many trees are selected because of their fall color potential, but they often do not provide good foliar color under the Southeast's climatic conditions.

A research project was initiated in 1980 at the AAES Piedmont Substation in Camp Hill to provide information about the important characteristics and adaptability of approximately 200 selected shade and ornamental tree species and cultivars. Information from 13 years of this project is presented for 60 of the native and exotic trees in Shade Trees for the Southeastern United States.

In addition to Williams, other authors include AU horticulture faculty Charles Gilliam, Gary Keever and Harry Ponder; John Owen, superintendent of the Piedmont Substation; and former research associate Donna Fare, who is now an assistant professor at Tennessee Technological University.

"There were several surprises in the study," Williams said. "For example, people think of oaks as being extremely slow growing, but one of the fastest-growing trees in the study was the sawtooth oak, a native of Asia that we found to grow 3.7 feet per year. Other oaks, such as white oak and shumard oak, were also found to grow faster than they had been given credit for."

Another surprise was the excellent performance of the bald cypress and pond cypress -- trees normally associated with swampy areas -- in both upland and lowland sites, he added.

"The honeylocust had been hailed as a good tree for urban landscaping, but the study revealed it's not a good tree for Alabama," Williams continued. "It's drought tolerant, but it's susceptible to several diseases and drops its leaves in the summer."

Similarly, several ornamental pear trees had been recommended to replace the popular Bradford pear, which has a weak branch structure that breaks with age. Cleveland, Capital, Whitehouse and Aristocrat pear trees do have stronger branches, but the AU study revealed they also are more susceptible to fireblight, a disease that can damage or kill trees. Bradford was the least susceptible of the flowering pears, Williams indicated.

To perform well in the urban landscape, a tree must be heat and drought tolerant and must adapt to Alabama's clay soil, he explained. Trees found to provide these characteristics included the Chinese pistache, Heritage river birch, Florida maple, and shumard, overcup and chestnut oaks.

"For those primarily interested in striking fall colors, ginkgo, red maple, flowering pear, Chinese pistache and shumard and scarlet oaks are excellent choices," Williams added. "Goldenraintree and Chinese flametree develop colorful flowers in the summer and interesting fruit in the fall."

Landowners who want to supplement the food supply for local deer populations should consider planting sawtooth, overcup or chestnut oaks. These oaks produce large crops of acorns, which deer love to eat, Williams said.

"The Auburn Shade Tree Evaluation is a non-irrigated trial, which makes it a realistic landscape situation. Trees are planted in both upland and lowland sites," he explained. "Trees that have performed well can be expected to do well in most of Alabama's typical landscape situations."

Shade Trees for the Southeastern United States, a 133-page, softcover book with more than 200 color photos, is available from the AAES Office of Research Information for $10 per copy. For more information, call Robyn Hearn at (205) 844-4877 or send check, money order, or purchase order to Research Information, 110 Comer Hall, Auburn University, Ala., 36849-5403.

-30-

News from:

Office of Ag Communications & Marketing

Auburn University College of Agriculture
Alabama Agricultural Experiment Station
3 Comer Hall, Auburn University
Auburn, AL 36849
334-844-4877 (PHONE) 334-844-5892 (FAX)

Contact Jamie Creamer, 334-844-2783 or jcreamer@auburn.edu
by Robyn Hearn

March 22, 1994